Potato is a tuber (that part carry out photosynthesis- the green color part seen in young potato). It is called a modified stem as it has scaly leaves, nodes, internodes, and adventitious roots, characteristic to stems. Potato tuber bears buds in small pits known as eyes. Buds develop to branches.

Onion is not an underground stem.

Modified stems can be categorized into three types:

• Underground – Rhizome, Bulb, Corm, Tuber.
• Subaerial – Runner, Sucker, Offsets, Stolon.
• Aerial – Tendrils, Thorn, Bulbils, Cladode, Phylloclade.

Stolon – Horizontal stems that run at or just below the soil surface with nodes that root and long internodes, the ends produce new plants. When above ground they are called “runners”. Tuber – An enlarged fleshy end of a stem, generally from rhizomes but often also referring to thickened roots too.

There are three types of stem: Underground stem, Aerial stem and Sub- aerial stem.

Potato grows on the end of the underground stem known as the stolon. – Potato is considered as a stem because it has many nodes called the eye and space between each eye is called the internodes. The eye of the potato can develop into a shoot and a new plant. Thus it is a stem vegetable.

Potato is considered as a stem vegetable because it grows in underground stems, known as stolons. Potato tubers are considered to be thick stems that have the buds sprouting stems and leaves. Roots do not possess the above mentioned attributes and hence, potato is considered as a stem and not a root.

Plants have leaves, roots, stem, flowers as their parts. We consume almost every part of the plant (root, stem, leaves, flowers, fruits, etc) as food. Fruits, vegetables, grains, seeds, herbs, are the foods we eat that are obtained from the plant sources.

The underground, edible root of a plant that is usually a long or round shaped tap root. Examples are carrot, turnip, swede, radish, parsnip, beetroot, celeriac, daikon radish and ginger.

Consider cassava, the shrub cultivated for its starchy, edible root, of which Nigeria is the world’s largest producer.